A hybrid vehicle may be provided with a driveline disconnect clutch. The driveline disconnect clutch may be closed to couple an engine with an electric machine. The driveline disconnect clutch may be opened to decouple the engine from the electric machine. The engine may provide torque to the driveline when the driveline disconnect clutch is closed. The engine is stopped when the driveline disconnect clutch is open to conserve fuel. The driveline disconnect clutch may be open during load conditions such as when a driver releases a brake pedal but does not apply an accelerator pedal and the vehicle creeps at a slow speed (e.g., 0-5 MPH). However, if the driver applies the accelerator pedal from a low load condition, the engine has to be started before positive engine torque can be applied to the driveline. Starting the engine may take more time than is desired, and a delay in driveline torque response may result.
The inventors herein have recognized the above-mentioned disadvantages and have developed a driveline operating method, comprising: providing torque to a driveline via a driveline integrated starter/generator in response to a desired torque; and starting an engine and idling the engine without providing engine torque to the driveline in response to the driver demand torque being within a threshold range of an engine cranking torque.
By providing torque to a driveline via a driveline integrated starter/generator at low driver demand torques, and starting the engine and allowing the engine to idle before the driver demand torque exceeds output capacity of the driveline integrated starter/generator, it may be possible to provide improved driveline torque response. Further, operating the engine at an efficient idle condition may only reduce fuel economy by a small amount.
The present description may provide several advantages. Specifically, the approach may improve driveline torque response. Further, the approach may have only a small effect on fuel economy. Further still, the approach allows the engine to remain off at low driver demand torque to improve fuel economy.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.